Facile Fabrication of Hierarchical SAPO-34 in Bifunctional Catalyst for Direct Conversion of Syngas into Light Olefins

Direct synthesis of light olefins from syngas (STO) using bifunctional catalyst composed of oxide and zeolite has attracted extensive attention in both academia and industry. In this study, we present a facile post-treatment approach to obtain hierarchical SAPO-34 by treating the crystallized product in mother liquor at low temperature. The physical and chemical properties of the resulting molecular sieves were characterized by XRD, SEM, TEM, N 2 adsorption–desorption, XRF and NH 3 -TPD. The obtained hierarchical SAPO-34 were mixed with ZnCrAlOx oxide to prepare the bifunctional catalyst, and the catalytic performance for direct conversion of syngas to light olefins was examined. Compared with the bifunctional catalyst obtained from the SAPO-34 molecular sieves without post-treatment, the bifunctional catalyst with hierarchical SAPO-34 obtained by mother liquor post-treatment showed enhanced performance with higher selectivity of light olefins. Importantly, the bifunctional catalyst with hierarchical SAPO-34 has a good catalytic stability with no obvious deactivation over 100 h of testing. The enhanced catalytic performance of the bifunctional catalyst with hierarchical SAPO-34 could be attributed to the hierarchical structure of SAPO-34 that can increase the rate of mass transfer to avoid further hydrogenation and conversion of olefin products on the catalyst, thus could improve the selectivity of C 2 –C 4 olefins. Graphical Abstract